Climate change, precipitation shifts and early summer drought: An irrigation tipping point for Finnish farmers?

In Finland early summer droughts are common. They cause yield losses ( YLoss ) of spring cereals, barley, oats and wheat, that cannot be compensated for later in the growing season. To support farmers in deciding whether to switch or not from rainfed to irrigated production, more data and understanding are needed on precipitation, its regional and interannual variation, caused YLoss and the cost-effectiveness of irrigation investments. This study aims to assess the spatiotemporal variation in early summer droughts and YLoss for spring cereals in the drought-prone Southwest Finland using past weather data (1971–2020). Furthermore, probability of early summer droughts was estimated based on two climate models, MPI-ESM and HadGEM2 and two greenhouse gas concentration scenarios, RCP4.5 and RCP8.5 for 2041–2070. Past data and future estimates of droughts were provided as 10 × 10 km 2 gridded data. A cost-benefit analysis was used retrospectively to estimate the feasibility of irrigation in 1991–2020. Two irrigation systems were found to be economically feasible for larger farm units and in the case of high farm yield levels. However, projected changes in future precipitation were not substantial for the critical yield determination phase of cereals. Hence, the change in precipitation per se does not necessarily encourage farmers to invest in irrigation in the future but further expanding farm size and higher future cereal yields might act as additional incentives. To conclude, this novel data on precipitation patterns, caused YLoss, and economic feasibility may promote irrigation as a key measure to reduce production uncertainties and yield variability in high-latitude conditions, although early summer droughts are not necessarily increasing.